1. Field of the Invention
This invention is generally related to coatings for implantable medical devices, such as drug delivery vascular stents.
2. Description of the State of the Art
Percutaneous coronary intervention (PCI) is a procedure for treating heart disease. A catheter assembly having a balloon portion is introduced percutaneously into the cardiovascular system of a patient via the brachial or femoral artery. The catheter assembly is advanced through the coronary vasculature until the balloon portion is positioned across the occlusive lesion. Once in position across the lesion, the balloon is inflated to a predetermined size to radially compress the atherosclerotic plaque of the lesion to remodel the lumen wall. The balloon is then deflated to a smaller profile to allow the catheter to be withdrawn from the patient's vasculature.
Problems associated with the above procedure include formation of intimal flaps or torn arterial linings which can collapse and occlude the blood conduit after the balloon is deflated. Moreover, thrombosis and restenosis of the artery may develop over several months after the procedure, which may require another angioplasty procedure or a surgical by-pass operation. To reduce the partial or total occlusion of the artery by the collapse of the arterial lining and to reduce the chance of thrombosis or restenosis, a stent is implanted in the artery to keep the artery open.
Drug delivery stents have reduced the incidence of in-stent restenosis (ISR) after PCI (see, e.g., Serruys, P. W., et al., J. Am. Coll. Cardiol. 39:393-399 (2002)), which has plagued interventional cardiology for more than a decade. However, ISR still poses a significant problem given the large volume of coronary interventions and their expanding use. The pathophysiological mechanism of ISR involves interactions between the cellular and acellular elements of the vessel wall and the blood. Damage to the endothelium during PCI constitutes a major factor for the development of ISR (see, e.g., Kipshidze, N., et al., J. Am. Coll. Cardiol. 44:733-739 (2004)).
The embodiments of the present invention address these concerns as well as others that are apparent to one having ordinary skill in the art.